Evaluation of a Non-Invasive Vocal Cord Vibration switch as an Alternative Access Pathway for an Individual With Hypotonic Cerebral Palsy – A Case Study
By Chan, Julie; Falk, Tiago H.; Teachman, Gail; Morin-McKee, Jennifer; Chau, Tom; Disability and Rehabilitation: Assistive Technology, Vol. 5, No. 1, pp. 69-78Publication Date: January 2010
Article outlines the development of a non-invasive vocal cord vibration switch for an individual with hypotonic cerebral palsy who utilized a voice-activated switch for computer access. The ‘throat vibration switch’ was designed to detect, in real time and measured by an accelerometer held against the surface of the throat, periodicities in vocal cord vibrations caused by vocalizations including hums and voiced sounds. The vibrations are measured along two axes, superior-inferior (SI) and anterior-posterior (AP), and output as voltages digitized and subsequently processed by a software algorithm. The switch has 3 inputs: SI and AP accelerometer signals and a threshold dial; and 2 outputs: a standard switch and a USB keyboard. A different signal is sent depending on the selected output: a high voltage for the standard switch and an F11 keystroke for the keyboard. When connected to the computer via USB, the F11 keystroke signal may be used to trigger scanning and choice selection in the WiViK virtual keyboard used by the recipient. The ‘throat vibration switch’ was evaluated against a commercially available voice activated switch, Words+ IST. Participant wrote sentences containing every letter of the alphabet, known as pangram sentences, with the two switches in 2 sessions per day over 4 days, with the order of the switches alternated and new sentences used each day. Perceived level of exertion was noted before and after each task and activation errors were logged for performance analysis. After using the device for 2 months, the user completed a qualitative survey with his educational assistant. The ‘throat vibration switch’ was found to outperform the voice activated switch in terms of sensitivity, speed, and user perceived exertion. Qualitatively, the user was more satisfied with the proposed switch relative to his existing solution.
Assistive Products Discussed: IST SWITCH
Published by: Taylor & Francis, Limited (Website:http://taylorandfrancis.org)
International Society of Physical and Rehabilitation Medicine (Web Site: http://www.isprm.org )
